Autoimmune diseases are characterized by autoantibodies that react with self-nuclear antigens such as uridine-rich RNAs and small nuclear ribonucleoproteins (snRNP). Prior work led to the hypothesis that snRNP-reactive T-cells provide help to anti-snRNP autoantibody producing B-cells. This work explores the cellular and molecular basis of human T-cell response to the B and D snRNP polypeptides of the Sm antigen. Mass spectrometry is used to characterize the polypeptides and other biomolecules under investigation in this study.